1. Technical Field
Embodiments of the present invention relate to a fixing device and an image forming apparatus, and more particularly, to a fixing device for fixing an image on a recording medium and an image forming apparatus incorporating the fixing device.
2. Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having two or more of copying, printing, scanning, facsimile, plotter, and other functions, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of a photoconductor; an optical writer emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a development device supplies toner to the electrostatic latent image formed on the photoconductor to render the electrostatic latent image visible as a toner image; the toner image is directly transferred from the photoconductor onto a recording medium or is indirectly transferred from the photoconductor onto a recording medium via an intermediate transfer belt; finally, a fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image to the recording medium, thus forming the image on the recording medium.
Such fixing device may include a fixing rotary body heated by a heater and an opposed body contacting the fixing rotary body to form a nip therebetween through which a recording medium bearing a toner image is conveyed. As the fixing rotary body and the opposed body rotate and convey the recording medium bearing the toner image through the nip, the fixing rotary body heated to a predetermined fixing temperature and the opposed body together heat and melt toner of the toner image, thus fixing the toner image to the recording medium.
Since the recording medium passing through the nip draws heat from the fixing rotary body, a temperature sensor detects the temperature of the fixing rotary body to maintain the fixing rotary body at a desired temperature. However, at each lateral end of the fixing rotary body in an axial direction thereof, the recording medium is not conveyed over the fixing rotary body, and therefore the recording medium does not draw heat from the fixing rotary body. Accordingly, after multiple recording media are conveyed through the nip continuously, a non-conveyance span provided at each lateral end of the fixing rotary body may overheat.
To address this circumstance, Japanese Patent Application Publication No. JP-2008-139779-A discloses a surface heating type fixing device that incorporates a shield member to shield the non-conveyance span of the fixing roller from the heater, thus preventing overheating of the fixing roller. The surface heating type fixing device includes a reflector having a slit to wrap around a halogen heater and be disposed such that the slit faces the fixing roller. The shield member is inserted into and removed from the slit of the reflector to the fixing roller within a light emitting path in which heat is emitted toward the fixing roller.